1. Field of the Invention
The invention relates to an integrated module having a delay element for setting a desired delay of a circuit-internal signal. The invention furthermore relates to a method for setting a temporal position of a signal in a signal path of a circuit of an integrated module to a desired signal position.
2. Description of the Related Art
Integrated circuits have signal paths carrying signals with respect to circuits. On account of interconnect lengths, line capacitances and the like, the circuit-internal signals experience a delay which cannot be determined exactly prior to the fabrication of the integrated circuit since, by way of example, the influence of the housing, of the leadframe, and of the process fluctuations cannot be determined exactly beforehand. It is often necessary, therefore, for the circuit-internal signals to be temporally adapted in such a way that their signal edges lie within predetermined time windows. Setup and hold times which prescribe a very precise temporal position of a signal edge exist particularly in the case of memory modules.
For this reason, in the integrated circuit, so-called delay chains are implemented in the signal path, which delay chains can be switched on or switched off in the signal path. By switching on the delay elements, it is possible to delay signals and, by switching off or bridging the delay elements, it is possible to accelerate the signals in the case where a delay element has previously been switched on. The switching-on and -off of the delay elements is carried out with the aid of an additional metalization mask in the fabrication process for the integrated circuit, the metalizations performed for switching a delay element into a signal path or, by means of a short-circuiting when bridging a delay element, not switching a delay element into the signal path.
The adaptation of the signal propagation time is carried out with the aid of a mask for all the integrated circuits of a processed substrate wafer. A subsequent change after the fabrication of the setting metalization is not possible in the case of processed components. By fabricating a new metal mask, it is possible to adapt subsequent fabricated integrated modules in accordance with altered timing conditions. An individual setting of the signal propagation time in an integrated module is not possible. Moreover, by virtue of the defined switching-on or -off of the delay elements in the signal path, it is no longer possible to take account of differences in the delay times of the delay elements brought about for example by process deviations or the like.